1. Field of the Invention
The present invention is directed to a system and a method for metrology of surface flatness and surface nanotopology of materials.
2. Description of Related Art
Numerous methods of measuring metrology of a surface are known. A common method is interferometry, which uses a reference beam and a target beam and the resulting interference pattern formed between the beams to determine the metrology. Another method is Hartmann wavefront sensing which determines the metrology through slope measurement indicative of wavefront error.
Both of these methods have related problems, including how to increase throughput, how to compensate for aberrations inherent in the system, and how to dynamically remove systematic tilt from the systems.
The present invention is therefore directed to metrology systems and methods which substantially overcomes one or more of the problems due to the limitations and disadvantages of the related art.
It is an object of the present invention to remove tilt from the measurements. It is another object of the present invention to remove optical aberrations of the system from the measurements. It is yet another object of the present invention to protect the elements in the system from damage. It is further another object of the present invention to increase throughput. It is another object of the present invention to increase accuracy, both during measurements and/or calibration.
At least one of the above and other objects may be realized by providing a metrology system including a pulsed light source, a mechanical assembly positioning a target relative to the pulsed light source, a wavefront sensor detecting light from the target to determine metrology of the target, and an optical assembly directing light from the pulsed light source to the target and from the target to the wavefront sensor.
The pulsed light source may output infrared radiation or ultraviolet radiation. When ultraviolet radiation is used, the wavefront sensor may include a Lumogen coating. The system may include a power monitor for the pulsed light source which dynamically monitors and adjusts power output by the pulsed light source. The system may include a spatial filter which spatially filters light output from the pulsed light source. The pulsed light source may output non-coherent light. The system may include a translation stage which continuously translates the target relative to the wavefront sensor.
At least one of the above and other objects may be realized by providing a metrology method including calibrating a system for measuring metrology of a target with a reference, measuring the metrology of the target, and using the calibrating to remove optical aberrations of the system from the measuring.
The calibrating may be performed before each measuring. When the measuring includes a plurality of frames, the calibrating may be performed between at least one adjacent pair of the plurality of frames. The calibrating may include acquiring multiple frames.
At least one of the above and other objects may be realized by providing a metrology system including a light source, a mechanical assembly positioning a target relative to the light source, a wavefront sensor detecting light from the target to determine metrology of the target, an optical assembly directing light from the light source to the target and from the target to the wavefront sensor, and a dynamic range filter between the target and the wavefront sensor which prevents damage to the wavefront sensor.
The wavefront sensor may include a processor performing at least one of a stitching algorithm, a centroid algorithm, look-up tables, and data pipelining. The optical assembly delivering light to and from the target may be shielded from the wavefront sensor. The wavefront sensor may measure wavefronts from the target at different wavelengths.
At least one of the above and other objects may be realized by providing a metrology system including a light source, a mechanical assembly positioning a target relative to the light source, a wavefront sensor detecting light from the target to determine metrology of the target, and an optical assembly directing light from the light source to the target and from the target to the wavefront sensor. The optical assembly includes a position sensor which detects incoming tilt from the light source and an optical steering mirror which directs light onto the target, the position sensor controlling the optical steering mirror to dynamically remove tilt.
At least one of the above and other objects may be realized by providing a metrology method including positioning a target relative to incoming light, positioning a detector relative to the target, directing light from the light source to the target and from the target to the detector, detecting an incoming tilt from the incoming light, adjusting the directing of the incoming light onto the target in accordance with the incoming tilt, and determining metrology of the target from light received by the detector.
These and other objects of the present invention will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating the preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.